The present invention relates in general to a lifting device and, in particular, to a device for lifting large containers.
More specifically, but without restriction to the particular use which is shown and described, a first embodiment of the present invention relates to a lifting device including an aperture and bearing surface that allows freight containers to be lifted and moved without limiting or restricting the interior volumetric space of the container. The mechanism which forms the aperture and bearing surface is mounted on the container so as to transfer the lifting forces into the container's structural frame.
Although it will be recognized that the present invention can facilitate lifting many different kinds of freight containers, the present invention has particular applicability to freight containers used as part of intermodal systems. In such systems freight containers are moved between destination points using two or more different modes of transportation. For example, a typical intermodal system moves freight containers on truck trailers and flat bed railroad cars. The freight containers used in intermodal systems are specifically designed to be interchangeable with different modes of transportation systems.
Freight containers commonly used heretofore in intermodal systems have employed a plurality of bearing mechanisms which extend or are built into the interior volumetric space of the container in the upper and/or lower corners within the container. These bearing mechanisms contain apertures which can be engaged by a variety of structures and devices suitable for lifting such containers.
One of the devices presently used to lift containers in intermodal transport systems may be described generally as a twist-lock bayonet mechanism. This known mechanism utilizes "T-shaped" lift members which are inserted through an oval aperture in castings positioned either on the sides or on top of the container. Once the flange of the T-shaped member is inserted through the aperture, it is rotated ninety degrees so that the axis of symmetry of the flange of the T-shaped member is aligned normal to the long axis of symmetry of the oval aperture. In this position, the T-shaped member bears against the lift casting to facilitate lifting of the container without disengagement.
One example of a twist-lock bayonet lifting mechanism using a rotatable T-shaped member is disclosed in U.S. Pat. No. 4,358,145, entitled: "Lifting Device For Container". This prior lifting mechanism, however, has at least the following principal disadvantages: (i) it is difficult to properly align the T-shaped member with the aperture of the bearing mechanism so that the T-shaped member may penetrate through the aperture without contacting the surface of the bearing mechanism, to avoid causing excessive wear on the surfaces of the T-shaped member or on the bearing mechanism; (ii) the T-shaped member must be rotatable, thus requiring a more complicated mechanical design; and (iii) the bearing mechanism containing the aperture must be fabricated with an internal cavity sealed from the interior space of the container to allow sufficient depth behind the aperture to permit the penetration of the T-shaped member and its rotation. Thus, existing bearing mechanisms of this type are constructed in a box-shape, and intrude into and reduce the interior volumetric space of the container.
Other previously known lift devices have employed lift members using elongated pills rather than rotatable T-shaped members. These lift members facilitate lifting of a container by insertion into bearing mechanisms located on the sides of the container. Such lift members, however, have no means of interlocking with the bearing lift casting to prevent inadvertent disengagement during lifting. The lift members, therefore, must be long enough and inserted to a depth beyond the aperture of the bearing mechanism so that during lifting, the container will not slide-off the end of the lift member. Such a device, therefore, requires that the bearing mechanism intrude upon and reduce the interior volumetric space of the container to an even greater degree than the bearing mechanism required for a lifting member of the known T-shape described above.
The present invention overcomes the disadvantages of the above noted existing devices by eliminating the need for a mechanism to rotate the end member, by avoiding intrusion on and reduction of the interior volumetric space of the container, and, also, by preventing inadvertent disengagement of the lift member from the bearing mechanism.
U.S. Pat. No. 3,567,266, entitled "Freight Container And Gripping And Lifting Attachment Therefore", illustrates an additional device for lifting freight containers. In that invention, a uniquely shaped socket is formed in a rectangular lift member affixed to a container in recessed portions of the container side walls. Lift blocks are inserted into the sockets. The lift blocks are shaped to fit within the sockets in a rotational manner so that the lift block is retained by the shape of the socket to prevent disengagement during lifting.
The present invention, however, represents an improvement over that shown in U.S. Pat. No. 3,567,266. First, the present invention eliminates the need for the rotational connection between the lift block and the lifting tongue. Second, the present invention eliminates the need both for a retainer gib in the socket and a shoulder on the lift block. This allows for easier tooling because the tolerance between the lifting member and the aperture of the present invention is greater, and the parts do not have to match as closely as in the invention disclosed in the patent. In addition, the construction of the present invention can be formed integral with the structural frame of the container, thus avoiding the need for recesses in the container side walls.